Swingarm concentric motor drive for electric motorcycle

ABSTRACT

A motorcycle includes an electric motor having an output shaft defining a motor axis, a rear wheel drivably coupled to the electric motor to propel the motorcycle, a swingarm rotatably supporting the rear wheel, and a frame. The frame includes a main frame member supporting the electric motor and the swingarm. A case of the electric motor is a stressed member of the frame between the main frame member and the swingarm. The swingarm is coupled to the case of the electric motor to define a swingarm pivot axis that is co-axial with the motor axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/789,302, filed on Jan. 7, 2019, the entire contents of which areincorporated by reference herein.

BACKGROUND

The present invention relates to vehicles, and more particularly relatesto motorcycles having a swingarm rear suspension and an electric drivemotor

SUMMARY

In one aspect, the invention provides a motorcycle including an electricmotor having an output shaft defining a motor axis, a rear wheeldrivably coupled to the electric motor to propel the motorcycle, aswingarm rotatably supporting the rear wheel, and a frame. The frameincludes a main frame member supporting the electric motor and theswingarm. A case of the electric motor is a stressed member of the framebetween the main frame member and the swingarm. The swingarm is coupledto the case of the electric motor to define a swingarm pivot axis thatis co-axial with the motor axis.

In another aspect, the invention provides a motorcycle including anelectric motor operable to propel the motorcycle, wherein a case of theelectric motor enclosing a rotor thereof is a stressed frame member ofthe motorcycle. A drivetrain of the motorcycle includes a drive sprocketrotatable by the electric motor, a driven sprocket coupled to a rearwheel of the motorcycle, and an endless drive member extended betweenthe drive sprocket and the driven sprocket. A swingarm supports the rearwheel, and a pivot axis of the swingarm on the motorcycle is also theaxis of rotation of both the drive sprocket and the rotor of theelectric motor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a motorcycle according to oneembodiment.

FIG. 2 is a right side view of the motorcycle of FIG. 1.

FIG. 3 is a left side view of the motorcycle of FIG. 1.

FIG. 4 is a perspective view of a portion of the motorcycle of FIG. 1,including a motor, a frame, and a swingarm.

FIG. 5 is an exploded assembly view of the portion of the motorcycleshown in FIG. 4.

FIG. 6 is a cross-section of the motorcycle, taken along line 6-6 ofFIG. 3.

FIG. 7 is a detail view of an output side of the motor, taken from thecross-section of FIG. 6.

DETAILED DESCRIPTION

Before any aspects of the invention are explained in detail, it is to beunderstood that the invention is not limited in its application to thedetails of construction and the arrangement of components set forth inthe following description or illustrated in the following drawings. Theinvention is capable of other embodiments and of being practiced or ofbeing carried out in various ways.

FIG. 1 illustrates a motorcycle 20 according to one embodiment of thepresent disclosure. The motorcycle 20 includes front and rear wheels 22,24 (e.g., a single front wheel 22 and a single rear wheel 24 alignedwith the front wheel 22 to define a single track). The motorcycle 20includes a frame structure having a main frame 28. A front fork 32supports the front wheel 22 ahead of the main frame 28. The front fork32 is rotatably coupled to a head tube 36 of the main frame 28.Handlebars 40 are coupled to the front fork 32 to allow a rider tocontrol the orientation of the front fork 32 and the front wheel 22. Arear swingarm 44 supports the rear wheel 24 for rotation therein, therear swingarm 44 enabling pivoting suspension movements of the rearwheel 24 and the swingarm 44 together relative to the main frame 28about an axis A (FIG. 4). In addition to the pivoting support at theaxis A, the swingarm 44 is coupled to the main frame 28 through a shockabsorber unit 46 (e.g., including a coil spring and a hydraulic damper).The motorcycle 20 further includes at least one seat 48 (e.g., saddleseat(s) for operator and optionally pillion passenger) and at least oneset of foot supports 50 (e.g., laterally extending foot pegs).

As illustrated, the motorcycle 20 is an electric motorcycle operable todrive by an electric powertrain including an electric power store 54(e.g., battery pack) and an electric motor 58 electrically coupled tothe power store 54 to convert stored electrical energy from the powerstore 54 into rotational kinetic energy for driving the motorcycle 20.As illustrated, the motor 58 powers the rear wheel 24 through an endlessdrive member 62 (e.g., belt or chain) in the form of a loop wrappedaround a drive sprocket 66 (FIG. 4) and a driven sprocket 68 that isfixedly secured to the rear wheel 24. As discussed in further detailbelow, the drive sprocket 66 that drives the endless drive member 62 ispositioned to rotate about the axis A. Further, the drive sprocket 66 isfixed to rotate integrally with an output shaft 70 of the electric motor58 about the axis A. As such, the motorcycle 20 is provided without amulti-speed transmission between the electric motor 58 and the drivesprocket 66, and without any gearbox whatsoever. This may further befacilitated by providing the electric motor 58 as a high pole countmotor having high torque density.

With particular reference to FIGS. 4 and 5, the electric motor 58 formsan integral stressed member of the motorcycle frame, which includes asthe primary member the main frame 28. The main frame 28 includes abackbone 28A extending rearward and downward from the head tube 36 and afront down tube 28B extending rearward and downward from the head tube36 below the backbone 28A. Both the backbone 28A and the front down tube28B are coupled rigidly to the electric motor 58 (e.g., at an outerperiphery thereof). The portions of the backbone 28A and the front downtube 28B connecting to the electric motor 58 are separate and spacedfrom each other to separately couple to the electric motor 58. Thebackbone 28A is directly coupled to the electric motor 58 (e.g., withmultiple fastener joints at a top of the motor), and the front down tube28B is coupled indirectly to the electric motor 58 (e.g., with anintermediate bracket 74 and a plurality of fasteners at a position onthe motor that is forward of the coupling of the backbone 28A). For thecoupling of the main frame 28, the electric motor 58 can be providedwith a plurality of bosses 76 as shown in FIG. 5 (e.g., bosses formed atthe radially outer edge of the motor and adapted to receive fastenersextending parallel with the axis A). However, one or more alternatecouplings can be used in addition to or in lieu of the illustratedbosses 76. The portion of the intermediate bracket 74 coupled to theelectric motor 58 is forked into spaced-apart left and right parts.Similarly, the bottom ends of both the back bone 28A and the front downtube 28B are also forked. It is also noted that, for example at a bottomportion thereof, the electric motor 58 provides one or more mountinglocations for the foot supports 50 such that the foot supports 50 dependfrom the electric motor 58 rather than another part of the frame such asthe main frame 28. As illustrated, the foot supports 50 include left andright foot pegs coupled to each other and to the electric motor 58 by acentral foot support bracket 78 extending between the foot supports 50.

Turning now to the swingarm 44, and referring particularly to FIGS. 5 to7, two pivoting joints between the swingarm 44 and the electric motor 58are formed with respective cylindrical bosses 82 of a motor housing orcase 84 provided to contain the motor's rotor 86. The rotor 86 is arotating assembly, for example including permanent magnets, that isdriven to rotate relative to a stator (not shown) and the motor case 84when the motor 58 is energized. The case 84 can be formed in multiplepieces that join together for assembly, for example parallel to the axisA. In some constructions, the motor case 84 may fully or partiallycontain power electronics for communicating electric power from thepower store 54 to the electric motor 58. The bosses 82 are formed toprotrude axially beyond axial end faces (e.g., flat or flat, ribbedplates) of the case 84. As such, the bosses 82 may form the widest pointof the case 84. As shown in FIGS. 6 and 7, the boss 82 on the drive side(rider's right as shown) may be formed as an insert separate from theportion of the case 84 that extends radially outward from the axis A tocover the rotor 86, although other constructions are optional. Theoutput shaft 70 exits through the boss 82 on the drive side. On thenon-drive side, the illustrated boss 82 is integrally formed with aportion of the case 84 that extends radially to the outer periphery ofthe case 84, and may also extend in a widthwise, axial direction overpart or all of the rotor 86. At each swingarm joint, a front forked endportion 90 of the swingarm 44 is joined with the respective boss 82(e.g., through a bearing 92 such as a roller bearing). Swingarm bearingclamps 94 are fastened to the front forked ends 90, around outer racesof the bearings 92, to retain the swingarm 44 in position relative tothe axis A. Each swingarm bearing clamp 94 includes features, such as achannel flanked by end flanges or shoulders, that position the swingarm44 to the motor 58 as shown in FIG. 7. By the arrangement shown anddescribed herein, the swingarm 44 is pivotably supported on the motorcase 84 about the axis A, which is the axis of the rotor 86 and theoutput shaft 70 of the motor 58, along with the drive sprocket 66. Loadsfrom the rear wheel 24 to the swingarm 44 are further transmitted to themain frame 28 only indirectly. In particular, loads at the swingarm 44are transmitted through two possible paths: through the shock absorberunit 46 to a shock absorber mount 28C of the main frame 28, and throughthe motor case 84 to the main frame 28.

The swingarm joint on the drive side, along with the drive sprocket 66,is concealed partially or wholly by a cover 96 (FIGS. 1 and 2) securedto the motor case 84, although the cover 96 is removed for clarity inFIGS. 4-7. An additional enclosure 100 (FIGS. 1-3) directly forward ofthe electric motor 58 contains power electronics for providing thedriving electric power signals to the motor 58. For example, one or anycombination of: the motor inverter, the charger, and the DC/DC convertermay be provided within the enclosure 100. The power electronicsenclosure 100 can be provided by one or more individual pieces coupledto the motor 58, thus forming a motor assembly or power unit withintegrated electronics.

As shown in FIG. 6, the rotor 86 within the motor 58 has across-sectional shape that is significantly wider in the axial directionat its outer radial ends, furthest from the axis A as compared with itsinner radial portion. For example, the rotor 86 may have thecross-sectional shape of an “I” when sectioned along the axis A (i.e., across-section, as FIG. 6, taken along a plane that contains the axis A).The axially-measured rotor width W is a function of radius thatincreases by a factor of 4, 5 or more in the radial direction from theinner portion of the rotor 86 that is secured to the output shaft 70 toa widest point adjacent the radial outer end. As shown in FIG. 6, thisshape creates large voids or pockets whereby first and/or secondbearings 104, 106 can be at least partially nested into the rotor 86(and in some cases fully nested therein). The first bearing 104 isprovided on a side of the rotor 86 opposite the drive side. The secondbearing 106 is provided on the drive side of the rotor 86, adjacent thedrive sprocket 66. The second bearing 106 can have a larger load ratingthan the first bearing 104. The second bearing 106 can have a greaterwidth than the first bearing 104 and/or a greater number of rows ofrolling elements therein (e.g., single row vs. multi-row). The first andsecond bearings 104, 106 are the only bearings supporting the outputshaft 70 relative to the case 84 and are positioned entirely within anexterior width profile of the case 84, even when measured to exclude theprojection of the bosses 82. In some constructions, as shown, the axialend faces of the case 84 are flat radially outward of the bosses 82, andthe first and second bearings 104, 106 are entirely between these twoflat axial end faces. As shown in FIG. 6, a sensor 108 (e.g., rotationalposition sensor) for the motor 58 is positioned within the boss 82 onthe non-drive side.

In the axial direction, the part of the swingarm 44 that is on the driveside is positioned between the adjacent axial end face of the motor case84 and the drive sprocket 66. In other words, the drive sprocket 66 ispositioned outboard of the swingarm pivot joint. A spacer ring 112 maybe provided axially between the drive sprocket 66 and the swingarm pivotjoint, and this may be the only component positioned axiallytherebetween. The spacer ring 112 can abut a shoulder on the outputshaft 70 to set the correct position of the drive sprocket 66 foralignment with the driven sprocket 68 on the rear wheel 24. A bolt 116threaded into the output shaft 70 secures the drive sprocket 66 to anaxial end of the output shaft 70, with or without a separate washer. Thedrive sprocket 66 is splined, keyed or otherwise locked for integralrotation with the output shaft 70.

The above-described construction provides for an electric motorcyclemotor 58 having an output axis A that is co-axial with the swingarmpivot axis. Furthermore, there is no separate pivot shaft for theswingarm 44 whatsoever, as the forward ends of the swingarm 44 interfacewith supporting portions (e.g., bosses 82) of the motor case 84, withonly bearings 92 therebetween. Pivoting the swingarm 44 co-axially withthe motor output axis A enables the motorcycle 20 to accommodate a widerange of suspension travel as it eliminates variation in center distancebetween the drive sprocket 66 and the driven sprocket 68 throughout thetravel of the swingarm 44. Tension in the endless drive member 62 doesnot vary with suspension travel, and this improves durability whileallowing the tension to be optimized for efficiency.

Various features and advantages of the invention are set forth in thefollowing claims.

What is claimed is:
 1. A motorcycle comprising: an electric motor havingan output shaft defining a motor axis; a rear wheel drivably coupled tothe electric motor to propel the motorcycle; a swingarm rotatablysupporting the rear wheel; and a frame including a main frame membersupporting the electric motor and the swingarm, wherein a case of theelectric motor is a stressed member of the frame between the main framemember and the swingarm, wherein the swingarm is coupled to the case ofthe electric motor to define a swingarm pivot axis that is co-axial withthe motor axis, and wherein the main frame member includes a backboneand a front down tube, the two of which are independently secured to anouter periphery of the case of the electric motor.
 2. The motorcycle ofclaim 1, wherein an end of the output shaft exits the motor case andsupports in fixed relation thereon a drive sprocket coupled to a drivensprocket of the rear wheel by an endless drive member.
 3. The motorcycleof claim 1, wherein a drive sprocket for driving the rear wheel throughan endless drive member is situated along the motor axis at a positionoutboard of the swingarm.
 4. The motorcycle of claim 1, wherein aforward end of the swingarm includes left and right sides joined to theelectric motor case with respective bearings to form respective swingarmpivots on the motor axis.
 5. The motorcycle of claim 4, wherein therespective bearings are enclosed by respective bearing clamps fastenedto the forward end of the swingarm.
 6. The motorcycle of claim 1,wherein a rotor of the electric motor has a cross-sectional shape of an“I” forming respective pockets on respective ends thereof, themotorcycle further comprising first and second bearings supporting therotor in the case of the electric motor, wherein the first and secondbearings are nested within the respective pockets of the rotor.
 7. Themotorcycle of claim 6, wherein the first bearing is remote from a driveside having a drive sprocket and the second bearing is adjacent thedrive side, the second bearing having a dimension along the pivot axisthat is larger than a similarly-measured dimension of the first bearing.8. The motorcycle of claim 1, further comprising a set of foot supportsdepending from the electric motor case.
 9. A motorcycle comprising: anelectric motor operable to propel the motorcycle, wherein a case of theelectric motor enclosing a rotor thereof is a stressed frame member ofthe motorcycle; a drivetrain including a drive sprocket rotatable by theelectric motor, a driven sprocket coupled to a rear wheel of themotorcycle, and an endless drive member extended between the drivesprocket and the driven sprocket; and a swingarm supporting the rearwheel, wherein a pivot axis of the swingarm on the motorcycle is alsothe axis of rotation of both the drive sprocket and the rotor of theelectric motor, and wherein the rotor has a cross-sectional shape of an“I” forming respective pockets on respective ends thereof, themotorcycle further comprising first and second bearings supporting therotor in the case of the electric motor, wherein the first and secondbearings are nested within the respective pockets of the rotor.
 10. Themotorcycle of claim 9, wherein the drive sprocket is mounted on anoutput shaft of the electric motor.
 11. The motorcycle of claim 9,wherein the drive sprocket is situated along the pivot axis at aposition outboard of the swingarm.
 12. The motorcycle of claim 9,wherein a forward end of the swingarm includes left and right sidesjoined to the electric motor case with respective bearings to formrespective swingarm pivots on the pivot axis.
 13. The motorcycle ofclaim 12, wherein the respective bearings forming the respectiveswingarm pivots are enclosed by respective bearing clamps fastened tothe forward end of the swingarm.
 14. The motorcycle of claim 9, whereinthe first bearing is remote from the drive sprocket and the secondbearing is adjacent the drive sprocket, the second bearing having adimension along the pivot axis that is larger than a similarly-measureddimension of the first bearing.
 15. The motorcycle of claim 9, furthercomprising a set of foot supports depending from the electric motorcase.
 16. A motorcycle comprising: an electric motor having an outputshaft defining a motor axis; a rear wheel drivably coupled to theelectric motor to propel the motorcycle; a swingarm rotatably supportingthe rear wheel; and a frame including a main frame member supporting theelectric motor and the swingarm, wherein a case of the electric motor isa stressed member of the frame between the main frame member and theswingarm, wherein the swingarm is coupled to the case of the electricmotor to define a swingarm pivot axis that is co-axial with the motoraxis, and wherein a rotor of the electric motor has a cross-sectionalshape of an “I” forming respective pockets on respective ends thereof,the motorcycle further comprising first and second bearings supportingthe rotor in the case of the electric motor, wherein the first andsecond bearings are nested within the respective pockets of the rotor.17. The motorcycle of claim 16, wherein the first bearing is remote froma drive side having a drive sprocket and the second bearing is adjacentthe drive side, the second bearing having a dimension along the pivotaxis that is larger than a similarly-measured dimension of the firstbearing.